# Elastic Critical Moment

EN 1993-1-1:2005+A1:2014 Clause 6.3.2.2 tells you to use $$M_{cr}$$ with no clues on how to calculate it. $$M_{cr}$$ is a purely theoretical value independent of any design code, so you can use any method you like to calculate it.

While any modern finite element package will calculate $$M_{cr}$$, some codes offer hand methods:

• BS 5950-1:1990 Clause B.2.2 (more recent versions of BS 5950 don’t give an explicit formula for $$M_{cr}$$, but it can be deduced)
• BS 5400-3:2000 Clause 9.7.5 (rearrange in terms of $$M_{cr}$$)
• PD 6695-2:2008+A1:2012 Clause 5.2 (equivalent to above BS5400 method)
• DD ENV 1993-1-1:1992 Clause F.1
• AS 5100.6-2017 Clause 5.6.1